Can you explain this on a more basic level? How does delegation work?
--Vicki
-----Original Message-----
From: Paul McNett [mailto:p@ulmcnett.com]
Sent: Wednesday, August 18, 2004 3:49 PM
To: wxPython-users@lists.wxwidgets.org
Subject: Re: [wxPython-users] Mix-in to base events?Chris Barker writes:
One other note: I used delegation (def __getattr__) so that all the
ordinary event attributes are available.
Stanfield, Vicki {D167~Indianapolis} wrote:
One other note: I used delegation (def __getattr__) so that all the ordinary event attributes are available.
Can you explain this on a more basic level? How does delegation work?
Here's some of the code from FloatCanvas:
# create a new event type
EVT_FC_LEFT_DOWN = wx.NewEventType()
...
# create a function for binding the event to a window
# NOTE: I can probably do without this, and use wxWindow.Bind() now.
def EVT_LEFT_DOWN( window, function ):
window.Connect( -1, -1,EVT_FC_LEFT_DOWN , function )
....
# create a class for all my mouse events:
class _MouseEvent(wx.PyCommandEvent):
"""
This event class takes a regular wxWindows mouse event as a parameter, and wraps it so that there is access to all the original methods. This is similar to subclassing, but you can't subclass a wxWindows event.
The goal is to be able to it just like a regular mouse event.
It adds the method:
GetCoords() , which returns and (x,y) tuple in world coordinates.
Another difference is that it is a CommandEvent, which propagates up the window hierarchy until it is handled.
"""
def __init__(self, EventType, NativeEvent, WinID, Coords = None):
wx.PyCommandEvent.__init__(self)
self.SetEventType( EventType )
self._NativeEvent = NativeEvent
self.Coords = Coords
def GetCoords(self):
return self.Coords
# this delegates all other attributes to the native event.
def __getattr__(self, name):
return getattr(self._NativeEvent, name)
# To create an instance of the _MouseEvent class:
def _RaiseMouseEvent(self, Event, EventType):
"""
This is called in various other places to raise a Mouse Event
"""
# this computes the "World Coordinates" from the mouse coords.
# This is the whole point of all this, so the user only has to
# deal with world coordinates.
pt = self.PixelToWorld( Event.GetPosition() )
evt = _MouseEvent(EventType, Event, self.GetId(), pt)
self.GetEventHandler().ProcessEvent(evt)
# this gets called when the native event happens"
def LeftDownEvent(self,event):
self._RaiseMouseEvent(event,EVT_FC_LEFT_DOWN)
-Chris
--
Christopher Barker, Ph.D.
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Chris.Barker@noaa.gov
Chris Barker wrote:
Here's some of the code from FloatCanvas:
# create a new event type
EVT_FC_LEFT_DOWN = wx.NewEventType()
...
For people who just want to create new events and handlers,
also check out wx.lib.newevent.
Roger